The present invention relates to an image signal magnifying apparatus capable of detecting missing subtitle which are lost when an image signal of letter box type, vista size, cinema size or the like, having missing upper and lower pictures, is magnified and displayed with an image display apparatus having an aspect ratio of 16 to 9 and the position of the subtitles is changed.
Recently, television receivers having large picture size are prevalent and it is also being considered to change the a picture screen of televisions to have a wide aspect ratio.
Further, video softwares (specifically, movie software) are sufficiently provided and an image magnifying apparatus which magnifies an image signal of letter box type, vista size, cinema size or the like, having missing upper and lower pictures, to a size corresponding to a picture screen with a wide aspect ratio (of 16 to 9, for example) to display the magnified image signal is commercially available. At this time, in a movie, after a subtitle processing has been made in which the subtitle is moved to an imaging unit to combine it with an image signal since the subtitle is lost, the image signal is magnified.
Referring now to the accompanying drawings, an example of an image magnifying apparatus provided with subtitle processing function used heretofore is described. FIG. 11 is a block diagram of an image magnifying apparatus provided with conventional subtitle processing function. In FIG. 11, numeral 13 denotes an input terminal for a current signal which is one output signal of a scanning line interpolation circuit 5 (refer to FIG. 1), 14 an input terminal for an interpolation signal which is the other output signal of the scanning line interpolation circuit 5, 6 a subtitle processing circuit, 41 an input terminal for a subtitle start line, 42 an input terminal for a subtitle end line, 43 an input terminal for the number of moving lines of the subtitle, 8 a combining circuit, 10 a double speed conversion circuit, 11 a D/A converter, 39 a image display unit, 40 a deflection pulse control circuit, 44 a horizontal synchronizing signal input terminal, and 45 a vertical synchronizing signal input terminal.
Operation of the image magnifying apparatus constructed above will now be described.
The subtitle processing circuit 6 detects a subtitle portion from the inputted current signal and the interpolation signal and moves the detected subtitle portion to a position determined by a user to combine the subtitle with an image signal. In this position, the subtitle signals detected from the current signal and the interpolation signal and the input image signal are combined in the combining circuit 8. The combined signal is converted at double speed and further converted from a digital signal into an analog signal. In the conventional method, the combined image signal is magnified by controlling a deflection pulse to display the image on the display unit 39.
FIG. 9 is a block diagram of the subtitle processing circuit 6. In FIG. 9, numeral 16 denotes an input terminal for the current signal, 17 an input terminal for the interpolation signal, 21 an input terminal of the subtitle start line, 22 an input terminal for the subtitle end line, 23 an input terminal of the number of moving lines of the subtitle, 18 a memory control signal generating circuit, 19 a field memory, 20 a gate circuit, 25 an output signal of a subtitle processing signal of the current signal, and 26 an output terminal of the subtitle processing signal of the interpolation signal. Operation of the circuit of FIG. 9 will now be described. The memory control signal generating circuit 18 generates a write enable pulse (WE signal) and a write reset pulse (RSTW signal) which are write control pulses for the field memory 19, on the basis of the start line and the end line for the subtitle inputted by the user. Then, the memory control signal generating circuit 18 generates a read enable pulse (RE signal) and a read reset pulse (RSTR signal), which are read pulses of the field memory 19, on the basis of the number of moving lines of the subtitle inputted by the user. Only the subtitle portions of the current signal and the interpolation signal are written in the field memory 19 and only the subtitle portions of the current signal and the interpolation signal are read from the field memory after delay of the number of moving lines designated by the user. The gate circuit 20 gates the output signals of the field memory 19 with the RE signal to nullify all of the signals to zero except the subtitle portion, so that the subtitle processing signals for the current signal and the interpolation signal are produced from the output terminals 25 and 26, respectively.
FIG. 10 is a block diagram of the combining circuit 8. In FIG. 10, numeral 27 denotes an input terminal of current line signal, 28 an input terminal of current line subtitle processing signal, 30 an input terminal of interpolation line signal, 31 an input terminal of interpolation line subtitle processing signal, 29 an input terminal of character detection pattern, 32 and 33 comparators, 34 and 35 switches, 36 an output terminal of current signal subtitle combining signal and 37 an output signal of interpolation signal subtitle processing signal. Operation of the circuit of FIG. 10 is now described.
The comparators 32 and 33 compare the subtitle processing signals and the character detection pattern to examine the magnitudes thereof. When the subtitle processing signals are larger than the character detection pattern, the comparators 32 and 33 produce O. When the subtitle processing signals are smaller, the comparators produce 1. The switches 34 and 35 effect switching of the image signal and the subtitle processing signal in response to the output signals of the comparators 32 and 33, to produce the subtitle combined signals of the current signal and the interpolation signal from the output terminals 36 and 37, respectively.
With the above configuration, however, there is a problem that since the magnification of image is made by controlling the deflection pulse, the density of scanning lines is coarse and characters of the subtitle are visually cut horizontally in a portion having no scanning line. Further, there is a problem in operability that the parameters required for the subtitle processing must be inputted by the user.